Performance of generalized soft-output demapper for LDPC-CFMT system over frequency selective fading channel

In this paper, we proposed the LDPC coded FMT systems and showed that the LDPC codes are effective to improve the bit error rate of FMT in frequency selective fading channel. When the LDPC codes are used for the FMT systems in mobile communications, especially in high bit rate applications, high bandwidth efficiency is required, and thus the high-order modulation is preferred. In this paper, we also propose a new soft decision metric generation method, which obviates the need of the noise variance estimation, for M-PSK/M-QAM modulation over frequency selective fading channel. Computer simulation indicates that there is no performance loss with our new metric, but the complexity of implementation is reduced.